Prince Philip has been moved to a different hospital and will continue to be treated for an infection.
A Buckingham Palace statement said: “The Duke of Edinburgh was today transferred from King Edward VII’s Hospital to St Bartholomew’s Hospital where doctors will continue to treat him for an infection, as well as undertake testing and observation for a pre-existing heart condition.
“The Duke remains comfortable and is responding to treatment but is expected to remain in hospital until at least the end of the week.”
His condition is not related to coronavirus.
Last week, Prince Edward told Sky News his father was doing “a lot better” and that the family were keeping their “fingers crossed”.
The prince said he was “looking forward to getting out, which is the most positive thing”.
Asked if the duke was frustrated, Prince Edward added: “Just a bit! I think that gets to all of us, and then, you can only watch the clock so many times and the walls are only so interesting.”
He was driven to the central London hospital on 16 February, with a royal source saying he walked in unaided.
Prince Charles was pictured in a face mask going to visit his father a few days later, and stayed for about half an hour.
The duke has received “some brilliant and lovely messages” from the public which have been passed on to him, said Prince Edward last week.
The last time he was in hospital was December 2019, when he spent four nights at the King Edward Hospital due to a “pre-existing condition”.
Philip retired in 2017 after decades of public duties and thousands of engagements and now rarely appears in public.
He was last seen in July 2020 when he transferred his role as colonel-in-chief of The Rifles to the Duchess of Cornwall.
He has been staying with the Queen at Windsor Castle since coronavirus restrictions were first introduced last year.
Earlier this month, the palace confirmed the they had both received their first dose of a vaccine.